Snail (Animal Class: Gastropoda) is probably the most overlooked trout food for the majority of anglers. Whether on rivers, spring creeks, or lakes/ponds, snails are abundant and trout do feed on them. Especially on spring creeks, but you might say "Who cares?" Well, trout do. Some anglers simply don't know it, others don't have the right flies. Almost every time I catch trout 11 to 15 inches on spring creeks in my area, when I do stomach sampling, I have been collecting snails more often than other types of food. Of course, when I do kick-seining, I collect them. The idea to design a snail pattern began ticking in my head.

Live sample from kick-seining

From a stomach sample, along with crustaceans.

Seasonal Importance:
Same observation can be applied as stated for cranefly larvae and Golden Stone nymphs. Even though these are present and available all year long, trout may pass up when other food sources are more abundant. During the periods when mayfly and caddis are actively hatching, trout simply pay more attention to them.

Mummy Snail

Development:

I first thought about how to represent the segmentations and flash of spiral coiled shell. Wire and Scud-back were employed. My next and biggest concern was the shape. If I would create the wider part at the rear end of hook-shank and taper down to the hook-eye, that would have been easier. However that would narrow the hook-gap and potentially result in lost fish. On the contrary, if I would design the wider part at the front end of hook, how could I wrap up the fly? The answer was to incorporate a bead. I could whip-finish behind the bead, maintaining the wide shape. Besides, the bead adds extra weight and all-time fishiness. It may even look like a "foot" peeking out! Finally it was created and tested on DePuy Spring Creek. It was an immediate success!! Since then it's been hauling in trout after trout. There are two reasons that I suspect for this great effectiveness:
1) nobody uses them and trout has never see snail flies
2) trout love them!!

*Match colors of Scud-back and dubbing according to what you find in waters you fish. In my case, brown dubbing with tan wrap was proven to be better than other colors.

How to Fish:

Use under an indicator rig in moderate to fast riffles where snails are dislodged and washed away. Apply split-shot to achieve desired depth (speed to get down) and drift (the more weight, the slower to drift). It's recommended to trail and fish together with other aquatic food imitations.

Crunchy?

Crushed Mummy Snail………..

Bad Snail:

New Zealand Mud Snail (Potamopyrgus antipodarum) is what we DON'T want. Please refer here for detailed information (http://en.wikipedia.org/wiki/New_Zealand_mud_snail) so we can identify them and somehow get rid of them. These bad snails combat against other trout food (mayfly nymphs and caddis larvae) over habitats and they usually take over. Consequently mayfly and caddis population of the water will decrease. Trout actually feed on Mud Snails but cannot digest them. Unfortunately in my area, the Madison Drainage (including Firehole and Gibbon Rivers within Yellowstone Park) are classified as "invaded". I once heard a very disgusting report from an angler who caught a brown trout for consumption from the Madison. As he gutted it he found a stomach full of tiny black snails…………
Fortunately, the Yellowstone River and its tributaries are invasion-free for now. So both local and visiting anglers are well-advised to wash wading boots and, if possible, own another pair and use one pair for each particular drainage.